Cesar Sayoc, 56, allegedly sent at least 14 pipe bombs to prominent figures, including former President Barack Obama and former Secretary of State Hillary Clinton.
Before the hearing, he appeared to get emotional while looking at someone seated in the courtroom. He remained handcuffed throughout his appearance.
After the judge read the charges against him and told him he had a right to remain silent, Sayoc quietly voiced a “yes” when asked if he understood.
Sayoc, who has New York ties and was born in Brooklyn, was arrested Friday in South Florida.
No decision has been made on Sayoc’s bond or extradition to New York where he was expected to face an initial set of charges connected to explosive device mailings found there.
A follow-up detention hearing was set for Friday morning in Miami.
He’s charged with interstate transportation of an explosive, illegal mailing of explosives, threats against former presidents and certain other persons, threatening interstate communications and assaulting current and former federal officers.
If convicted, he faces up to 48 years in prison.